Yasuyuki Nanamori

Rapid multi-target pointing and high accuracy attitude control steering law of variable speed control moment gyroscopes

In this study, to perform both a rapid attitude maneuver and a high accuracy control of an agile spacecraft, a Variable Speed Control Moment Gyroscope (VSCMG) steering law is proposed. In the proposed law, in order to maintain high manipulability and to control an internal disturbance of the VSCMG, initial gimbal angles of the VSCMG are optimized. In addition, the VSCMG acts like a classical CMG during the rapid attitude maneuver. During the high accuracy pointing control, the VSCMG acts like a Reaction Wheel (RW) to reduce the internal disturbance due to the gimbal motion. From the results of the numerical simulation, it was confirmed that the proposed law can control the agile spacecraft rapidly and high accuracy by switching several steering modes according to the attitude error of the spacecraft. In addition, the usefulness of the proposed law was confirmed in comparison with the steering law of Vadali for the rapid maltitarget acquisition and pointing control of the agile spacecraft.

Mode-Scheduling Steering Law of VSCMGs for Multi-Target Pointing and Agile Maneuver of a Spacecraft

This study proposes a method of selecting a set of gimbal angles in the final state and applies the method to the mode-scheduling steering law of variable-speed control moment gyros intended for multi-target pointing manoeuvres in the three-axis attitude control of a spacecraft. The proposed method selects reference final gimbal angles, considering the condition numbers of the Jacobian matrix of the reaction wheel mode in the final state of a single manoeuvre and that of the constant-speed control moment gyro mode at the start of the upcoming manoeuvre to keep away from the singularities. To improve the reachability of reference final gimbal angles, the nearest set of gimbal angles among nominated sets according to the Euclidean norm is selected as the reference final set at the middle of the single manoeuvre, and then realised by adopting gimbal angle feedback steering logic using null motion. In addition, the manoeuvre profile is designed such that the second half of the single manoeuvre is more gradual and takes longer than the first. Numerical simulation confirms the validity of the proposed method in consecutive manoeuvres.